Safety fuse



Feb. 18, 1930.

J. P. FERRITER ET AL r 1,747,231

SAFETY FUSE Filed June 20. 1927 ll/O' Patented Feb. 18, 1930 JOHN P. FERRITER, OF WATERTOWN, AND HENRY S. BACON, F FOREST HILLS, MASSACHUSETTS SAFETY FUSE Application filed June 20, 1927.

This invention relates to electrical fuses and protecting devices against lightning and other high voltages and excessive currents, particularly in telephone and telegraph installations.

The present practice is to use two separate units; one unit being a fuse, for protection against excessive currents, and another unit being a lightning arrestor, for protection against excessive voltages.

The object of this invention is to combine these two features in one unit, thereby mak ing the installation more compact and less costly. It is also proposed to facilitate the 1 clearing of troubles due to blown fuses or grounded lightning arrestors by confining the trouble to one unit instead of two, as in present installations.

In order to more clearly disclose the nature of the invention, certain embodiments thereof are disclosed in the accompanying drawing, in which a longitudinal cross-section view of the device is shown.

Referring more particularly to the drawing, the figure shows a cartridge type fuse container of the kind generally used in electrical installations, which may be of any desired size or material. The fuse body is shown cut away so as to show the component 50 parts of the device; namely the fuse fibre shell 2, a strip of fuse metal 3, the ends attached respectively to members 4 and 12, both of which are made of metal. A metal spring, 5, has one end fastened rigidly to member 4,

the spring itself pressing against a carbon plug 6, which rests in an insulating collar 7, being held rigidly therein by means of fusible cement 13. This cement may be a compound of anhydrous soda carbonate, pulverized quartz, water glass, and silica. The lower end of plug 6 is separated by a 0.003 inch spark gap clearance from a carbon disc 9 in the head of a removable plug 10 which contains the plug 6, collar 7, disc 9, so spaced as to form a spark gap 11. A ground plate 8 is arranged to contact with the disc 9 and plug 10. The fuse may be enclosed in an insulating medium if desired.

The fuse protecting device is placed in an electrical circuit, such as a telephone wire, in

Serial No. 200,234.

the usual manner, by mounting it in a receptacle so that one end of the wire composing the circuit connects at 4 and the other end of the wire connects at 12, the circuit being closed by fuse 3. Ground plate 8 is connected to the earth by a suitable contact in the receptacle.

As long as normal currents and voltages are applied to the circuit, current flows between 4 and 12 through the fuse 3. If an excessive current flows through the circuit, the fuse 3 is blown, opening the circuit. If an excessive voltage is applied to the circuit, the fusible cement 13 is melted, allowing the spring 5 to press the carbon plug 6 against the carbon disc 9, thus connecting the circuit to the earth through member 4, spring 5, plug 6, disc 9 and the ground plate 8. As the cement is not carried completely to the bottom of the carbon plug 6 and is in the form of a very thin film, it is forced upwards when fused and cannot flow between the contacts 6 and 9.

The arrangement of these components in one unit, is a valuable feature of the invention, as it permits of a much cheaper initial installation and is more economical of material used in maintenance and of time consumed in clearing troubles.

V e claim 1. In a device of the class described, a fibrous shell, a pair of end members fixed therein and a strip of fuse metal extending therebetween, a ground plate secured to the side wall of said shell, a removable plug arranged in said plate and shell, a carbon disc contained within said plug, a carbon plug held in spaced relation to said carbon disc to form a spark gap therebetween.

2. In a device of the class described, a fibrous shell, a pair of end members fixed therein and a strip of fuse metal extending therebetween, a ground plate secured to the side wall of said shell, a removable plug arranged in said plate and shell, a carbon disc contained within said plug, a carbon plug held in spaced relation to said carbon disc to form a spark gap therebetween, an insulating collar and fusible cement interposed between said carbon plug and the removable plug containing same.

3. In a device of the class described, a fibrous shell, a pair of end members fixed therein and a strip of fuse metal extending therebetween, a ground plate secured to the side Wall of said shell, a removable plug arranged in said plate and shell, a carbon disc contained Within said plug, a carbon plug held in spaced relation to said carbon disc to form a spark gap therebetween, an insulating collar and fusiblecement interposed between said carbon plug and the removable plug containing same, a spring attached to one of said end members and to said carbon button and adapted to force same into contact with said disc upon the fusing of said cement.

a. A fuse protecting device consisting of a single unit containing a strip of fuse metal for the protection of an electrical unit from the effects of an excess current, and a lightning arrestor consisting of a carbon button held inspaced relation With a carbon disc by means of removable plug containing fusible material arranged Within a ground plate'and a spring tending to force said button into contact with said disc for the purpose of the protection of an electrical circuit from the effects of excess voltages.

In testimony whereof We allix our signatures.

' JOHN P. FERRITER.

HENRY S. BACON. 

